Is there any way to tell the boot script to use the "-y" flag in fsck?
If something goes wrong with simple fsck, I always simply do a "fsck
-y". There is no other option for me. So, it would be VERY useful if
this could be done automatically instead of interrupting the router startup.
Thanks.
On 6/5/19 1:30 AM, Nick Holland wrote:
> On 6/4/19 1:29 PM, Mogens Jensen wrote:
>> I'm going to build a router for use in a remote location, and I have
>> chosen OpenBSD 6.5 for the task. Unfortunately, it's not possible to
>> protect the router with an UPS, so it will have to be resilient enough
>> to survive sudden power outages and still boot without manual
>> intervention.
>>
>> In the past I have built a few Linux based routers and they were
>> configured to run from RAM. I have made some research to see if this is
>> also possible on OpenBSD and found that, while there are solutions to
>> have / read-only, none of this is officially supported.
>>
>> Can anyone with experience running OpenBSD routers without UPS, tell if
>> filesystem corruption is going to be a problem after power outages, or
>> if there are any officially supported ways to make the system resilient
>> enough to not break after a power outage?
>>
>> I'm using an mSATA disk with MLC flash in the router.
>
> I realized a few decades ago that consumer UPSs are a bad investment.
> Industrial UPSs are a dubious idea in business unless you have a
> dual-power supply machine and can hook each PS to a DIFFERENT UPS -- in
> my area, grid power is more reliable than cheap UPSes (your mileage may
> vary). And you have to MAINTAIN your UPSs, otherwise after a few years,
> UPSs turn minor glitches into power outages (thank you very much).
>
> I'm also fond of proving my own claims, so I very often just yank the
> cord on my systems rather than doing orderly shutdowns.
>
> Yes, if you drop power on an OpenBSD system, you will get an fsck on
> reboot. Solution: Make your partitions as small as reasonable. Just
> because you got a 500G disk for cheap, no reason to allocate all 500G.
> For a router, 10G is PLENTY, and will fsck quickly. If you have slow
> media (i.e., flash drives), you might want to aim for 1G. Every once in
> a long while, you might catch a really bad time for the power to go out,
> and have to manually say "Fix it!" to fsck, but for the most part, the
> system will just come back up after the power comes back on.
>
> The less you write to disk, the less risk you have of having to manually
> intervene in your system's reboot. IF you want to do some fancy
> logging, keep the logging partition out of the fstab file, and have a
> script that brings it up with a "fsck -y" AFTER the system comes up, and
> start the fancy logging AFTER the big logging partition successfully mounts.
>
> But don't do stupid games to try to improve your chances, just make sure
> there's a monitor and keyboard available to fix any problems that might
> happen. Simple systems have simple problems. Complex systems break in
> complex ways. You want me to swear you'll never have to manually
> intervene in boot after an "event"? Nope. But I've walked
> non-technical people through single-user fsck's over the phone; when
> your bastardized system breaks, you will be down for a lot longer and
> you will be going on-site to fix.
>
> Nick.
>
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